The domain name system (DNS) is the way that internet domain names are located and translated into internet protocol addresses. The domain name system maps the name people use to locate a website to the IP address that a computer uses to locate a website. For example, if someone types TechTarget.com into a web browser, a server behind the scenes will map that name to the IP address 206.19.49.149.
The Domain Name System (DNS) translates internet domain and host names to IP addresses and vice versa.
On the internet, DNS automatically converts between the names we type in our Web browser address bar to the IP addresses of web servers hosting those sites. Larger corporations also use DNS to manage their company intranet. Home networks use DNS when accessing the internet but do not use it for managing the names of home computers.
How DNS Works
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DNS is a client/server network communication systems: DNS clients send requests to and receive responses from DNS servers. Requests containing a name that results in an IP address being returned from the server, are called forward DNS lookups. Requests containing an IP address and resulting in a name, called reverse DNS lookups, are also supported. DNS implements a distributed database to store this name and last-known address information for all public hosts on the internet.
The DNS database resides on a hierarchy of specialized database servers. When clients like web browsers issue requests involving internet hostnames, a piece of software (usually built into the network operating system) called the DNS resolver first contacts a DNS server to determine the server's IP address. If the DNS server does not contain the needed mapping, it will forward the request to a different DNS server at the next higher level in the hierarchy. After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the host eventually arrives at the resolver, that completes the request over Internet Protocol.
DNS additionally includes support for caching requests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients.
Setting up DNS on Personal Devices and Home Networks
Internet Service Providers (ISPs) maintain their DNS servers and use DHCP to configure their customer's networks automatically; Automatic DNS server assignment relieves households of the burden of DNS configuration. Home network administrators are not required to keep their ISPs settings, however. Some prefer to use one of the available public internet DNS services instead. Public DNS services offer better performance and reliability over what a typical ISP can reasonably offer.
Home broadband routers and other network gateway devices store primary, secondary, and tertiary DNS server IP addresses for the network and assign them to client devices as needed. Administrators can enter addresses manually or obtain them from DHCP. Addresses can also be updated on a client device via its operating system configuration menus.
Issues with DNS can be intermittent and difficult to troubleshoot given its geographically-distributed nature. Clients can still connect to their local network when DNS is broken, but they cannot reach remote devices by their name. When the network settings of a client device show DNS server addresses of 0.0.0.0, it indicates a failure with DNS or with its configuration on the local network.
Domain names are easy-to-remember words that we can use to tell a DNS server the website we want to visit. The Domain Name System (DNS) is what translates the friendly name to an IP address.
Somewhat like international phone numbers, the domain name system gives every server a memorable and easy-to-spell address, such as lifewire.com. The domain name hides the IP address that most people aren't interested in seeing or using, like the 151.101.129.121 address used by lifewire.com.
In other words, it's much easier to type 'lifewire.com' in your web browser than it is to remember and enter the IP address that the website uses. This is why domain names are so incredibly useful.
Examples of Internet Domain Names
Here are several examples of what's meant by a 'domain name:'
- lifewire.com
- nytimes.com
- navy.mil
- harvard.edu
- monster.ca
- wikipedia.org
- japantimes.co.jp
- dublin.ie
- gamesindustry.biz
- spain.info
- sourceforge.net
- wikipedia.org
In each of these instances, when you access the website using the domain name, the web browser communicates with the DNS server to understand the IP address that the websites use. The browser can then communicate directly with the web server using the IP address.
How Domain Names Are Spelled
Domain names are organized right to left, with general descriptors to the right, and specific descriptors to the left. It's like family surnames to the right and specific person names to the left. These descriptors are called 'domains'.
The top-level domain (i.e. TLD, or parent domain) is to the far right of a domain name. Mid-level domains (children and grandchildren) are in the middle. The machine name, often 'www', is to the far left. All of this combined is what's referred to as the Fully Qualified Domain Name.
Levels of domains are separated by periods, like this:
- Lifewire is the mid-level domain and .com is the top-level domain.
- japantimes is the smaller mid-level domain, .co is the larger mid-level domain, and .jp is the top-level domain.
- spain is the mid-level domain and .info is the top-level domain.
Tip
Most American servers use three-letter top-level domains (e.g. .com and .edu), while other countries commonly use two letters or a combination of two letters (e.g. .au, .ca, .co.jp).
A Domain Name Is Not the Same as a URL
To be technically correct, a domain name is commonly part of a larger internet address called a URL. The URL goes into much more detail than a domain name, providing more information like the specific folder and file on the server, the machine name, and the protocol language.
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Here are some examples of a URL with the domain name in bold:
- http://www.nytimes.com/2007/07/19/books/19potter.html
- http://www.nrl.navy.mill/content.php?P=MISSION
- http://www.fas.harvard.edu/~hsdept/chsi.html
- http://jobsearch.monster.ca/jobsearch.asp?q=denver&fn=&lid=&re=&cy=CA
- https://en.wikipedia.org/wiki/IAC_(company)
- http://classified.japantimes.co.jp/miscellaneous.htm
- http://www.dublin.ie/visitors.htm
- http://www.gamesindustry.biz/content_page.php?aid=26858
- http://www.spain.info/TourSpain/Destinos/
- http://azureus.sourceforge.net/download.php
Domain Name Problems
There could be a number of reasons behind why a website won't open when you type a particular domain name into the web browser:
- You typed the URL incorrectly see an error in a URL.
- The DNS server isn't working properly. Try changing the DNS server to a different one from our list of free and public DNS servers list.
- The website is down and there's nothing you can do to fix it.